METHOD FOR DIFFERENTIAL PRECODING AND BASE STATION SUPPORTING SAME

Description

[Technical Field]

[0001] The present invention relates to a wireless communication system, and more particularly, to differential precoding in a wireless communication system.

[Background Art]

[0002] The Fourth Generation (4G) communication system enabling the high-speed transmission of large-scale data uses an Orthogonal Frequency Division Multiplexing (OFDM) scheme or an Orthogonal Frequency Division Multiplexing Access (OFDMA) scheme. The OFDM scheme or the OFDMA scheme divides a bandwidth into a plurality of subcarriers to transmit data, and specifically, converts a serially input data row into N number of parallel data rows (where N is a natural number equal to or more than two) and carries the parallel data rows in the respective divided subcarriers, thereby increasing a data rate.

[0003] To enhance the efficiency of data transmission, a communication system using the OFDM scheme or the OFDMA scheme uses a Multi-Input Multi-Out (MIMO) scheme in which a base station including a plurality of antennas transmits different data through the respective antennas. By using the MIMO scheme, the communication system can obtain a diversity gain and moreover increase a data transmission rate.

[0004] Especially, by using the MIMO scheme, data or signals are simultaneously transmitted and received between a base station and a plurality of mobile stations. In such a Multi-User (MU) MIMO scheme, M number of antennas (where M is a natural number equal to or more than two) are arranged in a base station, and N number of antennas are arranged in a plurality of mobile stations. In this way, signals are respectively transmitted and received through the arranged antennas, thereby increasing a transmission rate.

[0005] As described above, a precoding technique may be applied to the MU-MIMO scheme, for minimizing inter-user interference and maximizing the sum rate.

[0006] Here, precoding is a type of techniques for enhancing the reliability of data transmission in a wireless communication system, and denotes a technique that generates a precoding matrix on the basis of information on fading and interference which occur in a channel in transmitting data, precodes data to be transmitted with the precoding matrix, and transmits the precoded data, thereby enhancing the reliability of data transmission.

[0007] However, since the 4G mobile communication system uses codebook having a limited size and reports channel information in the forms of Channel Quality Indicator (CQI), Rank Indicator (RI), and Precoding Matrix Indicator (PMI) at present, available precoding matrixes are limited, and thus, there are limitations in reducing inter-user interference and increasing the sum rate.

[0008] EP 1 91 098 A1 (NTT DOCOMO INC [JP]) 7 May 2008 (2008-05-07) discloses a base station:

• initializing a precoding matrix with a first codebook matrix index Feedback Popt for One-Shot codebook mode, wherein the One-Shot codebook depends on channel estimation
• updating recursively the precoding matrix with a second codebook matrix index Feedback Cmopt and a feedback bit indicator for absolute or differential precoding indication depending on the speed of channel change in tracking codebook mode, wherein the tracking codebook depends on channel estimation and the feedback bit indicator is used for switching between absolute and differential precoding depending on the mobility/doppler scenarios

[Technical Problem]

[0009] An aspect of the present invention is directed to a method for differential precoding and a base station supporting the same, which can reduce inter-user interference and increase the sum rate.

[0010] Another aspect of the present invention is directed to a method for differential precoding and a base station supporting the same, which can determine a precoding matrix with a plurality of codebooks.

[0011] Another aspect of the present invention is directed to a method for differential precoding and a base station supporting the same, which can adaptively determine a precoding matrix according to the change speed of a channel.

[0012] Another aspect of the present invention is directed to a method for differential precoding and a base station supporting the same, which can reduce overheads caused by the feedback of channel state information.

[0013] Additional advantages and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

[Technical Solution]

[0014] To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a method for differential precoding including: initializing a precoding matrix with a first (Precoding Matrix Indicator (PMI) for a channel between a mobile station and a base station; and updating the precoding matrix with a second PMI for the channel and side information for adaptively updating the precoding matrix according to a change speed of a state of the channel, wherein the side information has a quantized scalar value.

[0015] The method for differential precoding may further include: precoding downlink data with the initialized precoding matrix or the updated precoding matrix; and transmitting the precoded downlink data to the mobile station.

[0016] The precoding matrix may be initialized with the following Equation

where G(0) denotes a precoding matrix at an zeroth time, and F_main,q denotes a factor corresponding to the first PMI "q" in a main codebook.

[0017] The precoding matrix is repeatedly updated with the following Equation

where G(n) is a precoding matrix at an nth time, G(n-1) is a precoding matrix at an n-1 st time, F_sub,q denotes a factor corresponding to the second PMI "p" in a sub-codebook, * denotes an inter-matrix operator indicating one of a matrix addition, a matrix product, and a Kronecker product, and a denotes a value corresponding to the side information.

[0018] In another aspect of the present invention, there is provided a method for differential precoding including: precoding, when first Channel State Information (CSI) on a channel between a mobile station and a base station is received from the mobile station, first downlink data with a precoding matrix initialized with the first CSI to transmit the precoded first downlink data to the mobile station; updating, when second CSI on the channel and side information for adaptively updating the precoding matrix according to a change in a state of the channel are received from the mobile station, the precoding matrix with the side information and the second CSI; and precoding second downlink data with the updated precoding matrix to transmit the precoded second downlink data to the mobile station.

[0019] Each of the first and second CSI may be a PMI.

[0020] The method for differential precoding further includes: initializing the precoding matrix with a matrix corresponding to the first CSI in a first codebook; and performing a matrix product or a Kronecker product on the precoding matrix and a matrix raised to the power of the side information to update the precoding matrix, the matrix corresponding to the second CSI in a second codebook.

[0021] The side information may have a quantized scalar value.

[0022] Each of the first and second CSI may include at least one of a CQI and an RI.

[0023] In another aspect of the present invention, there is provided a method for differential precoding including: determining a first PMI indicating a first matrix selected from a first codebook, and feeding back the first PMI to a base station; determining a second PMI, indicating a second matrix selected from a second codebook, and side information that is used to extract the power of the second matrix, the side information being a quantized scalar value; and feeding back the second PMI and the side information to the base station periodically or aperiodically.

[0024] The method for differential precoding may further include receiving downlink data precoded with a precoding matrix initialized with the first matrix, or downlink data precoded with a precoding matrix updated with the precoding matrix and the second matrix raised to the power of the side information.

[0025] The updated precoding matrix may be calculated by performing a matrix product or a Kronecker product on the precoding matrix and the second matrix raised to the power of the side information.

[0026] In another aspect of the present invention, there is provided a base station including: a feedback receiver receiving first CSI, second CSI, and side information from a mobile station, the side information being used for adaptively updating a precoding matrix according to a change in a state of a channel; a precoder initializing the precoding matrix with the first CSI, repeatedly updating the precoding matrix with the second CSI and the side information, and precoding downlink data with the precoding matrix; and a data transmitter transmitting the downlink data to the mobile station.

[0027] The precoder includes: a precoding matrix initialization unit initializing the precoding matrix with Equation "G(0)=F_main,q"; and a precoding matrix update unit repeatedly updating the precoding matrix with Equation "G(n)=G(n-1)*(F_sub,p)^a"
where G(0) denotes a precoding matrix at an zeroth time, F_main,q denotes a factor corresponding to the first PMI "q" in a main codebook, G(n) is a precoding matrix at an nth time, G(n-1) is a precoding matrix at an n-1st time, F_sub,q denotes a factor corresponding to the second PMI "p" in a sub-codebook, * denotes an inter-matrix operator indicating one of a matrix addition, a matrix product, and a Kronecker product, and a denotes a value corresponding to the side information.

[0028] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

[Advantageous Effects]

[0029] According to embodiments, the present invention can reduce inter-user interference and increase the sum rate.

[0030] Moreover, the present invention can determine a precoding matrix with a plurality of codebooks, thus mitigating the restrictions of available precoding matrixes.

[0031] Moreover, by feeding back both channel information and side information, the present invention can adaptively determine a precoding matrix according to the change speed of a channel.

[0032] Moreover, the present invention can reduce overheads caused by the feedback of channel state information.

[Description of Drawings]

[0033] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. In the drawings:

FIG. 1 is a block diagram schematically illustrating a configuration of a base station that supports a differential precoding method in a wireless communication system, according to an embodiment of the present invention;

FIG. 2 is a block diagram schematically illustrating a configuration of a mobile station that supports the differential precoding method in the wireless communication system, according to an embodiment of the present invention; and

FIG. 3 is a flowchart illustrating the differential precoding method according to an embodiment of the present invention.

[Mode for Invention]

[0034] In the below description, for convenience of a description, a user and a terminal are used as the same concept, and a cell and a base station are used as the same concept.

[0035] In the specification, a description is made for exemplary embodiments of the present invention, and is not made for a single embodiment of the present invention. Also, in the below description, a description on a known structure or apparatus may not be provided for avoiding the ambiguousness of the core features of the present invention.

[0036] Moreover, in the below-described embodiments, each element or feature should be considered to be selective unless there is no clear statement. Therefore, each element or feature may be embodied without being combined with another element or feature, or the embodiments of the present may be configured by combing some elements or features. Also, in the embodiments of the present invention, the order of described operations may be changed, and some elements or features in a specific embodiment may be included in another embodiment or replaced with a corresponding element or feature in another embodiment.

[0037] Embodiments of the present invention will be described on a data transmission and reception relationship between a base station and a terminal. Here, the base station denotes a terminal node of a network that performs communication directly with the terminal. In the specification, a specific operation that is described as being performed by the base station may be performed by an upper node of the base station, depending on the case. That is, various operations, which are performed for communication with the terminal over a network configured with a plurality of network nodes including the base station, may be performed by the base station or the other network nodes other than the base station. The base station may be replaced by a term such as a fixed station, an Node B, an eNode B (eNB), or an access point, and the terminal may be replaced by a term such as user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS).

[0038] Moreover, a data transmission method and apparatus according to the present invention may be applied to various wireless access technologies such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), etc.

[0039] The wireless access technologies may be implemented as various wireless communication standard systems. For example, wideband CDMA (WCDMA) may be implemented as wireless technology such as Universal Terrestrial Radio Access Network (UTRAN) according to 3rd Generation Partnership Project (3GPP) standard organization. Also, CDMA2000 is CDMA-based wireless technology, and High Rate Packet Data (HRPD) according to 3rd Generation Partnership Project 2 (3GPP2) standard organization is wireless technology that provides a high packet data service in a CDMA2000-based system. evolved HRPD (eHRPD) is wireless technology in which HRPD has been advanced, and TDMA may be implemented as wireless technology such as Global System for Mobile communications (GSM)/ General Packet Radio Service (GPRS)/ Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented as wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, or EUTRAN (Evolved-UTRAN). Long Term Evolution (LTE) is a portion of Evolved-UMTS (E-UMTS) using E-UTRAN. LTE applies OFDMA in a downlink, and applies Single Carrier Frequency Division Multiple Access (SC-FDMA) in an uplink. LTE-Advanced (LTE-A) is wireless technology in which LTE has been advanced.

[0040] The MIMO system, to which present invention is applied, is a system that uses multi transmission antennas and at least one reception antenna. The present invention may be applied to various MIMO schemes. In the MIMO schemes, there are a spatial diversity scheme that transmits the same stream through multi layers, and a spatial multiplexing scheme that transmits a multi-stream through multi layers. In the spatial multiplexing scheme, a multi-stream being transmitted to one user denotes Single User-MIMO (SU-MIMO) or Spatial Division Multiple Access (SDMA). In the spatial multiplexing scheme, a multi-stream being transmitted to multi users denotes Multi User-MIMO (MU-MIMO). Also, each of the spatial diversity scheme and the spatial multiplexing scheme may be categorized into an open-loop scheme and a closed-loop scheme according to whether to use feedback information that is reported from users.

[0041] Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0042] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0043] FIG. 1 is a block diagram schematically illustrating a configuration of a base station included in a wireless communication system according to an embodiment of the present invention. A base station 200 according to the present invention may transmit data to multi users in an MIMO scheme. In this case, a plurality of transmission antennas 205 are arranged in the base station 200, and a plurality of antennas are arranged in each of a plurality of mobile stations 300. However, one antenna may be arranged in each mobile station 300.

[0044] As illustrated in FIG. 1, the base station 200 includes a scheduler 210, a precoder 220, a memory 230, a feedback receiver 240, and a data transmitter 250.

[0045] The scheduler 210 performs a scheduling operation for transmission of data received from an upper layer, in consideration of Channel State Information (CSI) fed back from each mobile station 300. Specifically, the scheduler 210 determines the Modulation and Coding Scheme (MCS) levels of downlink data to be transmitted to the respective mobile stations 300 in consideration of the CSI fed back from each mobile station 300, and provides the downlink data to the precoder 220.

[0046] In an embodiment, the CSI fed back from each mobile station 300 may be a Precoding Matrix Indicator (PMI). In another embodiment, the CSI may further include Channel Quality Indicator (CQI) and a Rank Indicator (RI).

[0047] In the following description, for convenience, the CSI is assumed as being the PMI.

[0048] The precoder 220 determines a precoding matrix, and precodes downlink data supplied from scheduler 210 with the determined precoding matrix. The precoder 220 includes a precoding matrix initialization unit and a precoding matrix update unit.

[0049] When a first PMI that is the initial PMI is fed back from the mobile station 300, the precoding matrix initialization unit initializes the precoding matrix with a factor corresponding to the first PMI in a first codebook stored in the memory 230. That is, when the first PMI is fed back, the precoding matrix initialization unit initializes the precoding matrix as expressed in Equation (1).

where G(n) denotes a precoding matrix at an nth time, G(0) is an initialized precoding matrix, and F_main,q denotes a factor corresponding to the first PMI "q" in a main codebook that is the first codebook.

[0050] Subsequently, the precoding matrix initialization unit precodes downlink data with the initialized precoding matrix, provides the precoded downlink data to the data transmitter 250, and stores the initialized precoding matrix in the memory 230.

[0051] Subsequently, the precoding matrix update unit updates the initialized precoding matrix, or repeatedly updates the updated precoding matrix periodically or aperiodically.

[0052] In detail, when both side information and a second PMI are periodically or aperiodically fed back from the mobile station 300, the precoding matrix update unit updates the initialized precoding matrix or a precoding matrix (hereinafter referred to as a previous precoding matrix) applied to previous downlink data, by using the side information, and a factor that corresponds to a second PMI in a second codebook stored in the memory 230.

[0053] Here, the side information is a value determined by the mobile station 300 such that a precoding matrix to be finally applied to downlink data is appropriately updated according to the change in a channel state, and may be a quantized scalar value.

[0054] In an embodiment, the precoding matrix update unit performs a matrix addition, a matrix product, or a Kronecker product on the initialized precoding matrix (or the previous precoding matrix) and a factor (corresponding to the second PMI in the second codebook) raised to the power of a value (corresponding to the side information), thereby updating the initialized precoding matrix (or the previous precoding matrix).

[0055] This is expressed as the following Equation (2).

where G(n) is a precoding matrix at an nth time and denotes a precoding matrix at a current time, G(n-1) is a precoding matrix at an n-1st time and denotes the previous precoding matrix, F_sub,q denotes a factor corresponding to the second PMI "p" in a sub-codebook that is the second codebook, * denotes an inter-matrix operator such as a matrix addition, a matrix product, or the Kronecker product, and a denotes a value corresponding to the side information.

[0056] Subsequently, the precoding matrix update unit precodes downlink data with the updated precoding matrix, provides the precoded downlink data to the data transmitter 250, and stores the updated precoding matrix in the memory 230.

[0057] As described above, since the base station 200 according to the present invention reflects the side information (which is fed back from the mobile station 300) in the factor corresponding to the second PMI in the form of the power, the base station 200 can adaptively adjust the change width of a precoding matrix according to the change speed of a channel state, and moreover reduce a steady-state error between the optimal precoding matrix and an actually calculated precoding matrix.

[0058] In the above-described embodiment, the precoding matrix initialization unit and the precoding matrix update unit have been described as different elements, but are not limited thereto. In a modification embodiment, the precoding matrix initialization unit and the precoding matrix update unit may be implemented as one body.

[0059] The memory 230 stores the precoding matrix (for example, the initialized precoding matrix and the updated precoding matrix) determined by the precoder 220, the first codebook, and the second codebook. In the present embodiment, the memory has been described as storing two codebooks, but is not limited thereto. In a modification embodiment, when two or more codebooks are used, the memory may store the two or more codebooks.

[0060] In an embodiment, the first codebook stored in the memory 230 may be an Re1-8 type of codebook, and the second codebook may be a sub-codebook determined from the first codebook.

[0061] The feedback receiver 240 receives feedback information from each mobile station 310, and provides the feedback information to the scheduler 210 and the precoder 220.

[0062] As described above, the feedback information fed back from each mobile station 300 to the feedback receiver 240 includes the first and second PMIs and the side information, and moreover may include the CQI indicating CSI and the RI indicating rank information.

[0063] The data transmitter 250 provides the precoded downlink data to the respective mobile stations 300 through the transmission antennas 2005.

[0064] FIG. 2 is a block diagram schematically illustrating a configuration of a mobile station that supports the differential precoding method in the wireless communication system, according to an embodiment of the present invention. Each of the mobile stations 300 according to the present invention includes a processor 310, a memory 320, and a Radio Frequency (RF) unit 330.

[0065] The processor 310 receives a reference signal from the base station 200, and estimates a channel between the base station 200 and the mobile station 300 with the received reference signal. The processor 310 selects one of precoding matrixes included in the first codebook shared between the mobile station 300 and the base station 200 according to the channel estimation result, and determines a first PMI indicating the selected first precoding matrix.

[0066] Moreover, the processor 310 selects one of precoding matrixes included in the second codebook periodically or aperiodically according to the channel-state change between the base station 200 and the terminal 300, and determines a second PMI indicating the selected precoding matrix. Here, as in the first codebook, the second codebook is shared in advance between the base station 200 and the mobile station 300.

[0067] In determining the second PMI, the processor 310 may determine side information that enables the appropriate update of a precoding matrix to be applied to downlink data according to the change speed of a channel state. Here, the side information may be a quantized scalar value.

[0068] When the channel state is rapidly changed, the side information leads to the increase in the change width of a precoding matrix to be finally applied to downlink data. When the channel state is slowly changed, the side information leads to the decrease in the change width of the precoding matrix to be finally applied to the downlink data.

[0069] In addition, layers of wireless interface protocols may be implemented by the processor 310.

[0070] The memory 320 is connected to the processor 310, and stores various information for driving the processor 310, the first and second PMIs, the first and second codebooks, etc.

[0071] The RF unit 330 is connected to the processor 310, and feeds back the first and second PMIs and the side information to the base station 200 or transmits uplink data to the base station 200.

[0072] Moreover, the RF unit 330 receives downlink data from the base station 200, and transfers the downlink data to the processor 310.

[0073] In the above-described embodiments, the processor 310 may include an Application-Specific Integrated Circuit (ASIC), a different chipset, a logic circuit, a data processing apparatus, and/or a converter that reciprocally converts a baseband signal and an RF signal.

[0074] Each of the memories 230 and 320 may include a Read-Only Memory (ROM), a Random Access Memory (RAM), a flash memory, a memory card, a storage medium, and/or a different storage device. The RF unit 330 may include one or more antennas transmitting and/or receiving the RF signal.

[0075] Hereinafter, the differential precoding method according to the present invention will be described in detail.

[0076] FIG. 3 is a flowchart illustrating the differential precoding method according to an embodiment of the present invention.

[0077] As illustrated in FIG. 3, a mobile station selects one matrix from a first codebook in consideration of a channel state in operation S300, determines a first PMI indicating the selected matrix in operation S310, and transmits the first PMI to a base station in operation S320. Here, the first codebook is shared in advance between the base station and the mobile station.

[0078] Subsequently, the base station determines an initial precoding matrix corresponding to the first PMI in the first codebook in operation S330.

[0079] Subsequently, the base station precodes downlink data with the initial precoding matrix in operation S340, and transmits the precoded downlink data to the mobile station in operation S350.

[0080] Subsequently, the mobile station selects one precoding matrix from a second codebook periodically or aperiodically, and determines side information for updating the precoding matrix at the base station in operation S360. Here, the second codebook is shared in advance between the base station and the mobile station.

[0081] In an embodiment, the side information may be a quantized scalar value, and a value of the side information may be determined in consideration of the change speed of a channel state. For example, the side information may be set to have a value that allows the update width of a precoding matrix to increase when the channel state is rapidly changed and, when the channel state is slowly changed, allows the update width of the precoding matrix to decrease.

[0082] Subsequently, the mobile station determines a second PMI indicating the one precoding matrix selected from the second codebook in operation S370, and transmits both the determined second PMI and the side information to the base station in operation S380.

[0083] In the above-described embodiment, it has been described that the side information is determined and then the second PMI is determined, but the present embodiment is not limited thereto. In a modification embodiment, the second PMI may be determined and then the side information may be determined, or the second PMI and the side information may be determined simultaneously.

[0084] Subsequently, the base station updates the initial precoding matrix with the side information and a matrix which corresponds to the second PMI in the second codebook, in operation S390. Specifically, as expressed in Equation (2), the base station performs a matrix product or a Kronecker product on the initial precoding matrix and a matrix raised to the power of the value of the side information, thereby updating the initial precoding matrix.

[0085] Subsequently, the base station precodes downlink data with the updated precoding matrix in operation S400, and transmits the precoded downlink data in the mobile station in operation S350.

[0086] Subsequently, by repeatedly performing operations S360 to S400, the updated precoding matrix is repeatedly updated.

[0087] That is, it has been described in operation S390 that the initial precoding matrix is updated, but, in a repeated operation, a previously updated precoding matrix is again updated with the side information and the matrix corresponding to the second PMI.

[0088] The above-described differential precoding method may be implemented in the form of a program executable with various computer means, in which case a program for executing a frame transmission method using pecoding for supporting MU-MIMO is stored in a computer-readable record medium such as a hard disk, a CD-ROM, a DVD, a ROM, a RAM, or a flash memory.

Claims

1. A differential precoding method, comprising:

initializing a precoding matrix with a first Precoding Matrix Indicator

PMI for a

channel between a mobile station and a base station; and

updating the precoding matrix with a second PMI for the channel and side information for adaptively updating the precoding matrix according to a change speed of a state of the channel,

wherein the side information has a quantized scalar value, and

wherein the precoding matrix is repeatedly updated with the following Equation

where G(n) is a precoding matrix at an nth time, G(n-1) is a precoding matrix at an n-1st time, F_sub,p denotes a factor corresponding to the second PMI "p" in a sub-codebook, * denotes an inter-matrix operator indicating one of a matrix addition, a matrix product, and a Kronecker product, and "a" denotes a value corresponding to the side information.

2. The differential precoding method of claim 1, further comprising:

precoding downlink data with the initialized precoding matrix or the updated precoding matrix; and

transmitting the precoded downlink data to the mobile station.

3. The differential precoding method of claim 1, wherein the precoding matrix is initialized with the following Equation

where G(0) denotes a precoding matrix at an zeroth time, and F_main,q denotes a factor corresponding to the first PMI "q" in a main codebook.

4. A differential precoding method, comprising:

precoding, when first Channel State Information CSI on a channel between a mobile station and a base station is received from the mobile station, first downlink data with a precoding matrix initialized with the first CSI to transmit the precoded first downlink data to the mobile station;

updating, when second CSI for the channel and side information for adaptively updating the precoding matrix according to a change in a state of the channel are received from the mobile station, the precoding matrix with the side information and the second CSI; and

precoding second downlink data with the updated precoding matrix to transmit the precoded second downlink data to the mobile station,

wherein the precoding matrix is initialized with a matrix corresponding to the first CSI in a first codebook, and

wherein the precoding matrix is updated by performing a matrix product or a Kronecker product between the precoding matrix and a matrix raised to the power of the side information, the matrix corresponding to the second CSI in a second codebook.

5. The differential precoding method of claim 4, wherein each of the first and second CSI is a PMI.

6. The differential precoding method of claim 4, wherein the side information has a quantized scalar value.

7. The differential precoding method of claim 4, wherein each of the first and second CSI comprises at least one of a CQI and an RI.

8. Abase station, comprising:

a feedback receiver receiving first CSI, second CSI, and side information from a mobile station, the side information being used for adaptively updating a precoding matrix according to a change in a state of a channel;

a precoder initializing the precoding matrix with the first CSI, repeatedly updating the precoding matrix with the second CSI and the side information, and precoding downlink data with the precoding matrix; and

a data transmitter transmitting the downlink data to the mobile station,

wherein the precoder comprises:

a precoding matrix initialization unit initializing the precoding matrix with Equation "G(0)=F_main,q"; and

a precoding matrix update unit repeatedly updating the precoding matrix with Equation "G(n)=G(n-1)*(F_sub,p)^a"

where G(0) denotes a precoding matrix at an zeroth time, F_main,q denotes a factor corresponding to the first PMI "q" in a main codebook, G(n) is a precoding matrix at an nth time, G(n-1) is a precoding matrix at an n-1st time, F_sub,p denotes a factor corresponding to the second PMI "p" in a sub-codebook, * denotes an inter-matrix operator indicating one of a matrix addition, a matrix product, and a Kronecker product, and "a" denotes a value corresponding to the side information.

9. The base station of claim 8, wherein each of the first and second CSI is a PMI.

10. The base station of claim 8, wherein the side information has a quantized scalar value.

Ansprüche

1. Differential-Vorcodierungsverfahren, das aufweist:

Initialisieren einer Vorcodierungsmatrix mit einem ersten Vorcodierungsmatrixindika-tor PMI für einen Kanal zwischen einer Mobilstation und einer Basisstation; und

Aktualisieren der Vorcodierungsmatrix mit einem zweiten PMI für den Kanal und Seiteninformationen zum adaptiven Aktualisieren der Vorcodierungsmatrix entsprechend einer Änderungsgeschwindigkeit eines Zustands des Kanals,

wobei die Seiteninformationen einen quantisierten Skalarwert aufweisen, und

wobei die Vorcodierungsmatrix mit der folgenden Gleichung wiederholt aktualisiert wird

wobei G(n) eine Vorcodierungsmatrix bei einem n-ten Mal ist, G(n-1) eine Vorcodierungsmatrix bei einem n-1-ten Mal ist, F_sub,p einen Faktor bezeichnet, der dem zweiten PMI "p" in einem Sub-Codebuch entspricht, * einen Intermatrixoperator bezeichnet, der eine Matrixaddition oder ein Matrixprodukt oder ein Kronecker-Produkt anzeigt, und

"a" einen Wert bezeichnet, der den Seiteninformationen entspricht.

2. Differential-Vorcodierungsverfahren nach Anspruch 1, das ferner aufweist:

Vorcodieren von Abwärtsstrecken-Daten mit der initialisierten Vorcodierungsmatrix oder der aktualisierten Vorcodierungsmatrix; und

Übertragen der vorcodierten Abwärtsstrecken-Daten zur Mobilstation.

3. Differential-Vorcodierungsverfahren nach Anspruch 1, wobei die Vorcodierungsmatrix mit der folgenden Gleichung initialisiert wird

wobei G(0) eine Vorcodierungsmatrix bei einem nullten Mal bezeichnet und F_main,q einen Faktor bezeichnet, der dem ersten PMI "q" in einem Hauptcodebuch entspricht.

4. Differential-Vorcodierungsverfahren, das aufweist:

Vorcodieren, wenn erste Kanalzustandsinformationen CSI auf einem Kanal zwischen einer Mobilstation und einer Basisstation von der Mobilstation empfangen werden, von ersten Abwärtsstrecken-Daten mit einer Vorcodierungsmatrix, die mit den ersten CSI initialisiert wird, um die vorcodierten ersten Abwärtsstrecken-Daten an die Mobilstation zu senden;

Aktualisieren, wenn zweite CSI für den Kanal und Seiteninformationen zum adaptiven Aktualisieren der Vorcodierungsmatrix entsprechend einer Änderung eines Zustands des Kanals von der Mobilstation empfangen werden, der Vorcodierungsmatrix mit den Seiteninformatiotlen und den zweiten CSI; und

Vorcodieren von zweiten Abwärtsstrecken-Daten mit der aktualisierten Vorcodierungsmatrix, um die vorcodierten zweiten Abwärtsstrecken-Daten an die Mobilstation zu senden,

wobei die Vorcodierungsmatrix mit einer Matrix initialisiert wird, die den ersten CSI in einem ersten Codebuch entspricht, und

wobei die Vorcodierungsmatrix durch Ausführen eines Matrixprodukts oder eines Kronecker-Produkts zwischen der Vorcodierungsmatrix und einer mit den Seiteninformationen potenzierten Matrix aktualisiert wird, wobei die Matrix den zweiten CSI in einem zweiten Codebuch entspricht.

5. Differential-Vorcodierungsverfahren nach Anspruch 4, wobei jede der ersten und zweiten CSI ein PMI ist.

6. Differential-Vorcodierungsverfahren nach Anspruch 4, wobei die Seiteninformationen einen quantisierten Skalarwert aufweisen.

7. Differential-Vorcodierungsverfahren nach Anspruch 4, wobei jede der ersten und zweiten CSI einen CQI und/oder ein RI aufweisen.

8. Basisstation, die aufweist:

einen Rückmeldungsempfänger, der erste CSI, zweite CSI und Seiteninformationen von einer Mobilstation empfängt, wobei die Seiteninformationen zum adaptiven Aktualisieren einer Vorcodierungsmatrix entsprechend einer Änderung eines Zustands eines Kanals verwendet werden;

einen Vorcodierer, der die Vorcodierungsmatrix mit den ersten CSI initialisiert, die Vorcodierungsmatrix mit den zweiten CSI und den Seiteninformationen wiederholt aktualisiert und Abwärtsstrecken-Daten mit der Vorcodierungsmatrix vorcodiert; und

einen Datensender, der die Abwärtsstrecken-Daten zur Mobilstation überträgt,

wobei der Vorcodierer aufweist:

eine Vorcodierungsmatrix-Initialisierungseinheit, die die Vorcodierungsmatrix mit der Gleichung initialisiert:

und

eine Vorcodierungsmatrix-Aktualisierungseinheit, die die Vorcodierungsmatrix mit der Gleichung wiederholt aktualisiert:

wobei G(0) eine Vorcodierungsmatrix bei einem nullten Mal bezeichnet, F_main,q einen Faktor bezeichnet, der dem ersten PMI "q" in einem Hauptcodebuch entspricht, G(n) eine Vorcodierungsmatrix bei einem n-ten Mal ist, G(n-1) eine Vorcodierungsmatrix bei einem n-1-ten Mal ist, F_sub,p einen Faktor bezeichnet, der dem zweiten PMI "p" in einem Sub-Codebuch entspricht, * einen Intermatrixoperator bezeichnet, der eine Matrixaddition oder ein Matrixprodukt oder ein Kronecker-Produkt anzeigt, und "a" einen Wert bezeichnet, der den Seiteninformationen entspricht.

9. Basisstation nach Anspruch 8, wobei jede der ersten und zweiten CSI ein PMI ist.

10. Basisstation nach Anspruch 8, wobei die Seiteninformationen einen quantisierten Skalarwert aufweisen.

Revendications

1. Procédé de pré-codage différentiel, comprenant :

l'initialisation d'une matrice de pré-codage au moyen d'un premier indicateur de matrice de pré-codage PMI pour un canal entre une station mobile et une station de base ; et

la mise à jour de la matrice de pré-codage au moyen d'un deuxième PMI pour le canal et d'une information auxiliaire pour la mise à jour adaptative de la matrice de pré-codage en fonction d'une vitesse de changement d'état du canal,

où l'information auxiliaire a une valeur de quantification scalaire, et

où la matrice de pré-codage est mise à jour de manière répétée au moyen de l'équation suivante :

où G(n) est une matrice de pré-codage à un n^ième moment, G(n-1) est une matrice de pré-codage à un n-1^ième moment, F_sub,p désigne un facteur correspondant au deuxième PMI "p" dans un sous-livre-code, * désigne un opérateur inter-matriciel indiquant soit une addition matricielle, soit un produit matriciel, soit un produit de Kronecker, et "a" désigne une valeur correspondant à l'information auxiliaire.

2. Procédé de pré-codage différentiel selon la revendication 1, comprenant en outre :

le pré-codage de données de liaison descendante au moyen de la matrice de pré-codage initialisée ou de la matrice de pré-codage mise à jour ; et

la transmission des données pré-codées de liaison descendante à la station mobile.

3. Procédé de pré-codage différentiel selon la revendication 1, où la matrice de pré-codage est initialisée au moyen de l'équation suivante :

où G(0) désigne une matrice de pré-codage à un moment zéro, et F_main,q désigne un facteur correspondant au premier PMI "q" dans un livre-code principal.

4. Procédé de pré-codage différentiel, comprenant :

le pré-codage, lorsqu'une première information d'état de canal CSI sur un canal entre une station mobile et une station de base est reçue de la station mobile, de premières données de liaison descendante au moyen d'une matrice de pré-codage initialisée au moyen de la première CSI pour transmettre les premières données pré-codées de liaison descendante à la station mobile ;

la mise à jour, lorsqu'une deuxième CSI pour le canal et une information auxiliaire pour la mise à jour adaptative de la matrice de pré-codage en fonction d'un changement d'état du canal sont reçues de la station mobile, de la matrice de pré-codage au moyen de l'information auxiliaire et de la deuxième CSI ; et

le pré-codage de deuxièmes données de liaison descendante au moyen de la matrice de pré-codage mise à jour pour transmettre les deuxièmes données pré-codées de liaison descendante à la station mobile,

la matrice de pré-codage étant initialisée au moyen d'une matrice correspondant à la première CSI dans un premier livre-code, et

la matrice de pré-codage étant mise à jour par réalisation d'un produit matriciel ou d'un produit de Kronecker entre la matrice de pré-codage et une matrice élevée à la puissance de l'information auxiliaire, la matrice correspondant à la deuxième CSI dans un deuxième livre-code.

5. Procédé de pré-codage différentiel selon la revendication 4, où la première et la deuxième CSI sont chacune un PMI.

6. Procédé de pré-codage différentiel selon la revendication 4, où l'information auxiliaire a une valeur de quantification scalaire.

7. Procédé de pré-codage différentiel selon la revendication 4, où la première et la deuxième CSI comprennent chacune un CQI et/ou un RI.

8. Station de base, comprenant:

un récepteur de retour d'information recevant une première CSI, une deuxième CSI et une information auxiliaire d'une station mobile, ladite information auxiliaire étant exploitée pour une mise à jour adaptative d'une matrice de pré-codage en fonction d'un changement d'état d'un canal ;

un pré-codeur initialisant la matrice de pré-codage au moyen de la première CSI, mettant à jour de manière répétée la matrice de pré-codage au moyen de la deuxième CSI et

de l'information auxiliaire, et pré-codant des données de liaison descendante au moyen de la matrice de pré-codage ; et

un transmetteur de données transmettant les données de liaison descendante à la station mobile,

où le pré-codeur comprend :

une unité d'initialisation de matrice de pré-codage initialisant la matrice de pré-codage au moyen de l'équation :

et

une unité de mise à jour de matrice de pré-codage mettant à jour de manière répétée la matrice de pré-codage au moyen de l'équation : "G(n)=G(n-1)*(F_sub,p)^a" où G(0) désigne une matrice de pré-codage à un moment zéro, F_main,q désigne un facteur correspondant au premier PMI "q" dans un livre-code principal, G(n) est une matrice de pré-codage at à un n^ième moment, G(n-1) est une matrice de pré-codage à un n-1^ième moment, F_sub,p désigne un facteur correspondant au deuxième PMI "p" dans un sous-livre-code, * désigne un opérateur inter-matriciel indiquant soit une addition matricielle, soit un produit matriciel, soit un produit de Kronecker, et "a" désigne une valeur correspondant à l'information auxiliaire.

9. Station de base selon la revendication 8, où la première et la deuxième CSI sont chacune un PMI.

10. Station de base selon la revendication 8, où l'information auxiliaire a une valeur de quantification scalaire.

Drawing